1. Field of the Invention
The present invention relates to a projection-type image display device having a solid light source and a light valve, the projection-type image display device configured to cause light emitted from the solid light source to perform scanning on the light valve along a predetermined scanning line.
2. Description of the Related Art
Conventionally, there has been known a projection-type image display device which displays an image on a screen by irradiating a light valve with light emitted from a solid light source such as an LED (Light Emitting Diode) or an LD (Laser Diode). In addition, there has been also disclosed a technique that synchronizes an oscillation cycle of a pulse laser with a modulation cycle of a light valve when a solid light source is a pulse laser (see, for example, Japanese Patent Publication No. Heisei 11-305710 (claim 2, paragraph [0018], FIG. 1)).
A projection-type image display device displays an image on a screen by causing a spot of light emitted from a solid light source to perform scanning on a light valve along a predetermined scanning line. The light valve modulates light emitted from the solid light source to control an amount of light to be projected onto the screen. An output of the solid light source (that is, a voltage applied to the solid light source) is generally constant.
Here, an improvement in luminance of an image displayed on a screen is desired for a projection-type image display device. Meanwhile, under the condition that the output of the solid light source (that is, a voltage applied to the solid light source) is constant in the projection-type image display device, the contrast of an image tends to decline when luminance of the image displayed on the screen is low due to peripheral lighting effects or the like.